Conventionally, various methods have been proposed for detecting strain, damage, and the like in measurement subjects such as buildings. For example, deformation in a concrete wall of a structure such as a building causes serious damage to the building. Measuring using strain gauges or rulers is known as methods for monitoring the progression of such deformations. However, with these measuring methods, there is a possibility of variation (i.e. measurement error) in the values measured by a measurer, arising from the measurement methods in which strain gauges or rulers are used. Thus, the need to accurately detect deformations is not sufficiently met. In addition, with these measuring methods, it is necessary to perform the measuring near the measurement subject. Therefore, there is a need for a method that enables accurate and convenient deformation measuring, which does not require the measurer to be near the measurement subject.